Roberts was born in Rhinebeck, New York.[1] She is the daughter of actor Eric Roberts and Kelly Cunningham,[2] the stepdaughter of Eliza Roberts and Kelly Nickels, and the niece of actresses Julia Roberts and Lisa Roberts Gillan. Her paternal grandmother was Betty Lou Bredemus (1934-2015), and she also has a half sister, Grace.[3] During her childhood, Roberts spent time on the sets of her aunt Julia Roberts' films. These experiences sparked a desire in Emma, from the age of five, to follow her father and aunts into the film industry.[3] Her mother initially wanted her to have a normal childhood.[4]

She went on to appear in smaller roles in two family films: in 2002's Grand Champion, as the sister of the main character Buddy (Jacob Fisher); and in 2003's Spymate, as the kidnapped daughter of former secret agent Mike Muggins (Chris Potter), who tries to rescue her with the help of a spy monkey. Grand Champion had a brief theatrical release in August 2004,[6] while Spymate was not released until February 2006, when it was given a theatrical run in Canada,[7] followed by its DVD release in April 2006. In August 2003, Roberts was scheduled to shoot an independent film called Daisy Winters, starring as the title character, alongside Rachel Weisz.[8] However, the film, which would have been Roberts' first leading role, never began shooting due to financial problems.

In 2004, Roberts began[9] starring as the lead character Addie Singer in the Nickelodeon series Unfabulous, which debuted in September of that year. The sitcom earned Roberts a Teen Choice Award nomination and several Young Artist Award nominations.[10] The show aired for three seasons from 2004 to 2007 and aired 42 episodes, ultimately ending in December 2007. The television series focused on a seventh grader, Addie Singer (Roberts), and her two best friends. The show had had various TV movies, including The Perfect Moment. In 2004, Roberts guest-starred in an episode of the Nickelodeon series Drake and Josh in the episode "Honor Council". After her run on Unfabulous, Nickelodeon had considered giving Roberts a kickstart into a music career.[11]

In 2006, Roberts returned to the big screen, starring alongside Sara Paxton and singer JoJo in Aquamarine. She won a 2007 Young Artist Award for Best Supporting Young Actress in a Feature Film for her role in the film.[12] The film Aquamarine took fifth place at the box office in its opening weekend making $8 million.[13] In early 2006, Roberts finished shooting her title role in Nancy Drew. The film was released to theaters on June 15, 2007, and grossed over $7 million in its opening weekend,[14] though the film was not well received by critics.[15] Roberts was set to reunite with Nancy Drew director Andrew Fleming on both Rodeo Gal[16] and a Nancy Drew sequel in 2007, but these films were never made.[17][18] In 2008, she had her voiceover debut when she voiced the English version of the character Wilma in the CGI-animated family film The Flight Before Christmas.[19]

In 2009, Roberts starred alongside Jake T. Austin in Hotel for Dogs,[20] based on the novel by Lois Duncan. The film premiered in January 2009, and took fifth place in its opening weekend with over $17 million. The film has to-date grossed over $114 million, and received generally mixed reviews from critics.[21] Roberts starred as the lead in the film Wild Child,[22] about a rebellious teen from Malibu, California sent to a boarding school in England. Roberts described her character as "pretty much your typical spoiled-brat Malibu socialite who gets shipped off to British boarding school."[23] Roberts also appeared in the indie film Lymelife with Alec Baldwin, which was premiered at the 2008 Toronto International Film Festival. Roberts said that Lymelife is "kind of like American Beauty meets The Ice Storm,"[23] and that her reasoning for doing the film was that: "Some people look at me and think, 'She's just Julia Roberts' niece.' So I wanted to do something smaller and edgier, something that would show I really am an actress."[23]

In February 2012, Roberts began filming a new movie in Syracuse, New York titled Adult World. The film also took place in Syracuse and co-starred John Cusack and Evan Peters. Roberts played a recent college graduate who works at an adult bookstore to make ends meet. The actress has said that most of her lines were ad-libbed so her reactions in the film were completely genuine.[29] Roberts appears in a supporting role in Dustin Lance Black'sVirginia, which received a limited theatrical release in May 2012 after a two and a half year delay. She next appeared in the 2012 film Celeste and Jesse Forever, parodying pop stars such as Kesha with her performance as Riley Banks, an incurious blonde singer. Roberts said in an interview that her role as Banks tempted her to write an album of songs using her character as an alter ego.[30]

On February 7, 2013, The Hollywood Reporter confirmed that Roberts had been cast to star in a pilot for Fox called Delirium, based on the Lauren Oliver novels. Roberts portrayed Lena Haloway, the protagonist, but Fox decided not to pick up the show.[31][32] Roberts then starred in the comedy film We're the Millers, alongside Jennifer Aniston and Jason Sudeikis. It was released on August 7, 2013. The film received mixed reviews from critics and was a financial success, grossing over $269 million against a budget of $37 million.[33] She next appeared in the third season of the horror anthology series American Horror Story from late 2013 through January 2014. Roberts portrayed a self-involved party girl named Madison Montgomery, who also happens to be a telekinetic witch.[34] She then portrayed Maggie Esmerelda, a con artist posing as a fortune teller, in the fourth season, American Horror Story: Freak Show.

In 2005, Roberts released a debut album titled Unfabulous and More. The album was released on September 27, 2005, through Columbia Records and Nick Records. It also served as the soundtrack to the television series Unfabulous, in which Roberts starred. The album peaked at number 46 on Billboard '​s Top Heatseekers chart.[38] In September 2005, two promotional singles were released from the album: "I Wanna Be" and "Dummy". The album includes several original songs (among them "Dummy" and "I Wanna Be", both of which were also released as music videos, "I Have Arrived" and "This Is Me", which was co-written by Roberts), as well as some of Addie's songs from the first season, including "Punch Rocker" and "New Shoes" (both from the episode "The Party"), "94 Weeks (Metal Mouth Freak)" (from "The Bar Mitzvah") and "Mexican Wrestler" (which had previously appeared on Jill Sobule's 2000 album Pink Pearl and in the episode "The 66th Day" from Unfabulous). During the same year, Roberts recorded "If I Had It My Way" for the soundtrack of the 2005 Disney film Ice Princess. In 2006, Roberts covered the song "Island in the Sun", which was originally recorded by Weezer in 2001; she recorded the song for the Aquamarine soundtrack, a film in which she starred as one of the leads.

Roberts said in a 2007 interview: "Right now I am focusing on movies. I am getting ready to start a new movie this summer so that is taking a lot of my time. I think when I am a little bit older it is definitely something I'd like to pursue."[39] In another interview, she said: "My musical career is indefinitely on hold. I don't like people who become like 'actor slash singer.' I think people should be one or the other because usually you're not going to be great at both. You're going to better at one, so you might as well stick to the one you're good at. I'm going for acting."[40]

In February 2009, she was named the brand ambassador for Neutrogena, appearing in print and television ads for the company.[41] Roberts has also appeared multiple times as part of Teen Vogue '​s Best Dressed list, including June 2007, September 2008, December 2008 and February 2009.[42]

In September 2011, Roberts began attending Sarah Lawrence College but by January 2012, she had put her studies on hold to concentrate on work commitments.[43]

Roberts, who has previously dated actor Alex Pettyfer, Dathan Kuppin and actor Chord Overstreet,[43][44][45] began dating actor Evan Peters in 2012 after they worked together on the film Adult World.[46] In July 2013, while they were staying at a hotel in Montreal, Quebec, someone overheard a dispute coming from their room and called the police. After a "heated argument", they had begun hitting each other.[47] When the police arrived, they arrested Roberts. Peters was not arrested because Roberts did not have any immediately visible injuries.[48] Peters declined to press charges and Roberts was released several hours later.[49] In a joint statement, the couple called it "an unfortunate incident and misunderstanding," and stated that they "are working together to move past it."[49] They became engaged in December 2013.[50][51]